In the teaching of biology to primary and secondary school students it is essential if students are to have a good feel and understanding of the science that they have an opportunity to work with and utilize living materials. Most biology courses lack convenient living materials to use in their course work and, in addition, most biology courses use animal subjects predominately. At an elementary and secondary school level, it is generally considered impractical to teach general or advance courses in botany, genetics, science education, or applied plant sciences because of the difficulty in finding suitable living plant material that would permit students to explore plant growth development, physiology, reproduction, genetics, evolution and ecology. Such studies are normally difficult to perform in an educational setting because the life cycle of most plants is of sufficiently long duration that multiple generations cannot conveniently be grown during any time period convenient to an educational schedule.
Traditionally one of the difficulties in performing research or breeding development in plant species is the long time periods necessary to perform breeding projects in plant species. Since genetic experiments typically require many generations of individuals with appropriately selected cross-breeding among individuals with particular traits, many years of work are necessary if only one, or a relatively few generations, of plants complete their life cycle during any given year. Accordingly, it was perceived as useful to generate plants which would have a shorter life cycle, so that more generations of plants could be grown up and selectively cross-bred in a shorter period of time.
A series of short life cycle plants, referred to as rapid-cycling plants, has been developed for plants in the family Cruciferae. Plants of this family are familiarly referred to as Crucifers because of the four petalled flowers, which are deemed to resemble a cross or crucifix. The Crucifer family is so large that it is broken into sub-groups, referred to as tribes. One of the tribes of Crucifer plants is the Brassicae tribe. The genus Brassica includes a variety of plants of commercial utility, such as mustard, brussel sprouts, cabbage, kale, cauliflower, broccoli, and rape. A related genus is Raphanus which is represented in commercial crop species by the radish. Rapid cycling sub-populations have been generated in populations of the genus Brassica as well as the genus Raphanus. The cytogenetic interrelationships among six Brassica species and Raphanus are illustrated graphically by the following chart, in which cytoplasmic genome is designated by capital letters and nuclear genome is designated by lower case letters, and where a indicates 10, b indicates 8 and c and r indicate 9 chromosomes. ##STR1##
A rapid cycling population of plants has been developed for each of these species (not for Raphanobrassica). Each of the populations grows rapidly and flowers in a time period of between sixteen and thirty days. Plants of these rapid-cycling populations average, depending on the species, between sixteen and thirty days to flower, between thirty-six and sixty days for an entire plant life cycle and between eighteen and one hundred and seven seeds produced from each plant. This allows for these population of plants to be cycled over six and ten successive generations per year.
Stocks of rapid cycling Brassica plants are maintained by the Crucifer Genetics Cooperative, 1630 Linden Drive, University of Wisconsin, Madison, Wis. 53706. The Cooperative publishes a Resource Book describing the manipulation and handling of fast cycling Crucifer stock and also maintains seed reserves of the stocks. Seeds are readily available to anyone interested in Brassica botany or genetics by application for membership to the cooperative, which is open to all. Stocks of the plants are thus readily available and obtainable and maintained indefinitely by the Cooperative.